sections: AR (as-received), AC1 (ageing 300°C/1000h) and AC2 (ageing 300°C/5000h). The mechanical properties at room temperature determined for the ...
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ScienceDirect Procedia Engineering 66 (2013) 226 – 232
5th Fatigue Design Conference, Fatigue Design 2013
Influence of temperature and long term ageing on the fatigue crack growth in a precipitation hardened martensitic stainless steel. L. Dimithe Aboumoua, b,*, G. Henaffa, M. Arzaghia, S. Pommierb a
Pprime Insitute,UPR CNRS 3346, ISAE-ENSMA, University of Poitiers, Department of physics and mechanics of materials, 1.av. Clément Ader, 86961 Chasseneuil-Futuroscope, France b LMT, UMR 8535, ENS-Cachan, 61. av. du président Wilson, 94230 Cachan, France.
Abstract The high-temperature Fatigue Crack Growth (FCG) behaviour of a 15-5 PH (precipitation-hardened) martensitic stainless steel was investigated in three different metallurgical conditions, i.e., as-received, aged at 300°C for 1000h and 5000h. FCG tests were conducted at room temperature and 300°C under constant amplitude loading with two load ratios (R = 0.1 and 0.7) and under variable amplitude loading. The results indicate that the fatigue crack growth rates (FCGRs) increase with R-ratio at the lower ΔK regime and merge together in the high ΔK regime, regardless of ageing conditions and temperature. At 300°C, the FCGRs are higher than at room temperature for all ageing conditions. Under variable amplitude loading, the same retardation effect was observed for all the given ageing conditions at room temperature © The Authors. Authors.Published PublishedbybyElsevier Elsevier Ltd. © 2013 2013 The Ltd. Open access under CC BY-NC-ND license. Selection and of of CETIM Selection and peer-review peer-reviewunder underresponsibility responsibility CETIM, Direction de l'Agence de Programme. Keywords: Fatigue crack growth, temperature, thermal ageing;
1. Introduction The precipitation-hardened stainless steel has both a natural property of corrosion resistance and high strength. Especially, the 15-5 PH martensitic stainless steel, which contains about 15% of Cr and 5% of Ni, is a high strength material due to the formation of Cu precipitates. Thanks to its high performances, the material has been introduced into heavily loaded structural elements for which a high level of reliability is required in chemical, aircraft, naval and nuclear industries. In addition, this material is also considered for the development of the engine pylons, which are designed using a damage tolerance approach. In service, the engine pylon that transmits loads
1877-7058 © 2013 The Authors. Published by Elsevier Ltd. Open access under CC BY-NC-ND license. Selection and peer-review under responsibility of CETIM doi:10.1016/j.proeng.2013.12.077
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L. Dimithe Aboumou et al. / Procedia Engineering 66 (2013) 226 – 232
between the engines and the wing is exposed to high temperatures and is subjected to variable amplitude cyclic loading. Indeed, the temperature can varies from -40°C on cruise to 300°C or even 400°C during take-off. Ageing due to this prolonged thermal exposure may have an impact on the fatigue crack growth rate resistance of the material. Furthermore, information on the FCG behaviour under variable amplitude loading is required. Indeed, if a substantial retardation is present, it has to be taken into account in order to prevent over-conservative predictions. The point is that fatigue crack growth data on the 15-5PH-type steel are not widespread in literature. Some data about the 17-4 PH stainless steel are available; they are however mainly focused on the influence of heat-treatments and related microstructural characteristics on the room-temperature fatigue properties [2-10]. Studies on the hightemperature FCG behaviour are much more limited and do not consider the effects of variable amplitude loading and long-term ageing. The present study was thus undertaken within the framework of a national program in order to investigate the influence of the temperature (300°C) and long-term ageing on the FCG behaviour of 15-5PH steel under constant amplitude loadings and repeated overloads. The objective is to develop a model that can take into account the respective influence of these different phenomenons. More precisely, the present paper reports the experimental fatigue crack growth results obtained so far considering three metallurgical conditions, namely the as-received condition and two ageing conditions. 2. Material and experimental procedures The material used in the current study is a particular grade of 15-5PH (reference name: X15U5W) stainless steels supplied by AUBERT & DUVAL in the form of a rectangular-section bar. The section of bar was 140mm x 60mm. This material was solution treated at 1040°C for 30min and then heat treated at 505°C for 4h. The chemical composition of this steel in wt% is 0.025 C, 0.38 Si, 0.80 Mn,
